The extent of remediation of contaminated sediments in Superfund sites will be related to local and more widespread impacts. What are the impacts of the sediments on the benthic organisms at the site? Are the sediments providing a source of toxic metals that causes adverse impacts to water column organisms? Are toxic metals being transferred to higher trophic level organisms where they can pose a potential human hazard? This proposal addresses a portion of each question. The major focus is to develop a model for the flux of cadmium and chromium to and from sediments. The conventional formulation uses linear partitioning to establish the particulate and dissolved concentrations in the sediment. However, the partitioning of cadmium is controlled by the quantity of AVS in the sediment. Significant dissolved concentrations appear only after the solid phase concentration exceeds the AVS. In addition, metal can be released by oxidation of reduced solid phases of cadmium and chromium either in the aerobic sediment layer or in the overlying water. The experiments being proposed are aimed at quantifying the effect of aerobic and anaerobic layer processes on the flux of cadmium and chromium. Dissolved and particulate fluxes will be examined. A resuspension device that produces homogeneous turbulence is available for the latter experiments. Benthic macrofauna will be added to the reactors to measure the enhancement. The kinetics of particulate oxidation in the overlying water will be investigated. The goal of the project is to construct a comprehensive model of cadmium and chromium sediment fluxes and particle oxidation. Additionally it is proposed to test whether the relationship discovered in the present Superfund project - that the acute toxicity of cadmium and nickel in sediments can be predicted from the sediment acid volatile sulfide concentration (AVS) can also predict chronic, or at least sublethal effects in benthic organisms. The induction of metallothionein will be examined using benthic organisms from Foundry Cove.